Database
[{"business_id":"1022","dt_op":ISODate("2018-10-02"),"transactions":[{"Product name":"Rose","Quantity":10},{"Product name":"Orange","Quantity":20},{"Product name":"Apple","Quantity":15}]}]
Query
db.collection.aggregate([{$match:{business_id:"1022"}},{$unwind:"$transactions"},{$group:{_id:"$transactions.Product name",TotalSum:{$sum:"$transactions.Quantity"}}}])